Both still images and moving images have become of high quality in recent years. This has ever been increasing an amount of information to be handled by users. In view of this, studies have been widely conducted on how to increase an in-plane recording density, in order to advance mass storage of magnetic recording devices called hard disk drives (HDDs). One promising technique of high-density magnetic recording can be represented by a discrete track medium, which is a magnetic recording medium including magnetic recording tracks magnetically separated from one another by nonmagnetic guide sections. The discrete track medium has a configuration which almost completely prevents magnetic interaction between magnetic particles along track edges. This reduces medium noise and thus greatly improves recording density. The following further describes this point.
A magnetic layer formed uniformly (continuously) in an in-plane direction of a medium as in some conventional magnetic recording mediums causes a magnetic transition region to be formed at a boundary between recording marks on adjacent tracks. This blurs the boundary between such recording marks on adjacent tracks and thus causes noise. A smaller track pitch does not result in a smaller magnetic transition region at the boundary between recording marks on adjacent tracks, and thus causes noise to be large relative to signals. In consequence, a smaller track pitch leads to a smaller signal-to-noise ratio (S/N ratio). By contrast, in a case of a discrete track medium, which records magnetic information on its magnetic recording tracks magnetically separated from one another, a recording mark has a track edge corresponding to an edge of a magnetic recording track. This allows for achievement of a relatively high S/N ratio even when the track pitch is small, unlike in the above conventional magnetic recording mediums. As a result, discrete track mediums achieve a recording density higher than that of other conventional magnetic recording mediums.
Patent Literatures 1, 2, and 3, for example, disclose techniques for discrete track mediums described above. Patent Literature 1 discloses a discrete track medium storing information tracked by magnetic reproduction elements which are provided so as to collectively bridge a nonmagnetic portion from a magnetic recording region to another. Patent Literature 2 discloses a discrete track medium including: data signal recording regions; and tracking servo signal recording regions developed from a conventional tracking servo pattern. In the case of Patent Literature 3, each track includes a signal gap. Detecting such a signal gap on an adjacent track allows tracking to be performed.
Patent Literature 1, in particular, requires two magnetic reproduction elements provided side by side so as to collectively bridge a nonmagnetic portion from a magnetic recording region to another. Patent Literature 1 allows for tracking by obtaining a difference between signals received by the two magnetic reproduction elements, respectively. This necessitates providing not only an element for reproducing magnetic information but also two other magnetic reproduction elements for tracking, the magnetic reproduction elements collectively bridging a nonmagnetic portion from a magnetic recording region to another.